Film drive mechanism

ABSTRACT

THE OUTPUT SHAFT OF A FILM DRIVE IS ROTATED THROUGH A FIXED ANGLE EACH TIME AN ELECTRIC MOTOR IS ENERGIZED INDEPENDENTLY OF THE NUMBER OF REVOLUTIONS OF THE MOTOR. WHEN THE MOTOR IS ENERGIZED, A PINION ON THE MOTOR SHAFT ENGAGES A SPUR HAVING AN INTERRUPTED TOOTHED PERIPHERY. THE SPUR GEAR IS HELD BY A PAWL IN AN INITIAL POSITION SO THAT UPON ENERGIZATION OF THE MOTOR, THE PINION TURNS THE GEAR THROUGH A FIXED ANGLE AT WHICH POINT THE INTERRUPTED PERIPHERY OF THE GEAR BECOMES ALIGNED WITH THE PINION STOPPING FURTHER ROTATION OF THE GEAR. THE PAWL COOPERATES WITH THE PINION AND GEAR TO MAINTAIN THE GEAR IN ITS NEW POSITION AS LONG AS THE MOTOR REMAINS ENERGIZED. AFTER THE MOTOR IS DE-ENERGIZED, THE PAWL IS EFFECTIVE TO RETURN THE GEAR TO ITS ORIGINAL POSITION.

1971 GALLINA 3,552,234

FILM DRIVE MECHANISM Filed April 4, 1969 2 Sheets-Sheet 1 /0 v 6 /5 20 CONTROL .L

DEV/CE W L/GHT 47 SOURCE 1/2 rl FILM MAGNET/C CUE 44070? p DETECTOR 1; j, I I I l 2 A, 20 y /4 /9 PROJECT/0N LENS /3 FIG.

v INVENTOR HAROLD GALL/NA ATTORNEY Jan.5, 1971s Y H. GALLINA 3,552,234

FILM DRIVE MECHANISM Filed April 4, 1969 2 Sheets-Sheet 2 i aa A m5 INVENTOR HAROLD GALL/NA j (g WM ATTORNEY 3,552,234 FILM DRIVE MECHANISM Harold Gallina, Belleville, N.J., assignor to Elco Corporation, Willow Grove, Pa., a corporation of Dela ware Filed Apr. 4, 1969, Ser. No. 813,589 Int. Cl. G03b 1/38 US. Cl. 74820 12 Claims ABSTRACT OF THE DISCLOSURE The output shaft of a film drive .is rotated through a fixed angle each time an electric motor is energized independently of the number of revolutions of the motor. When the motor is energized, a pinion on the motor shaft engages a spur gear having an interrupted toothed periphery. The spur gear is held by a pawl in an initial position so that upon energization of the motor, the pinion turns the gear through a fixed angle at which point the interrupted periphery of the gear becomes aligned with the pinion stopping further rotation of the gear. The pawl cooperates with the pinion and gear to maintain the gear in its new position as long as the motor remains energized. After the motor is de-energized, the pawl is effective to return the gear to its original position.

This invention relates to a drive mechanism for indexing an output shaft through a fixed angle each time an input shaft is rotated.

The output of a drive mechanism of the type described is ideally suited to index a sprocket wheel or pawl of a film strip projector, and thus advance a frame of the film strip into alignment with the framing aperture of the projector. To maintain framing each time the strip is advanced, it is essential for the sprocket wheel or pawl to be driven through precisely the same displacement each time the drive is called upon to advance the film. Conventionally, a Geneva drive mechanism is utilized as the output of the drive.

It is also essential to advance the strip as quietly and rapidly as possible; and to this end, it is conventional to employ the shaft of a high speed electric motor as the input to the film drive mechanism. In some well-known conventional film drive mechanisms, the motor is energized upon the detection of a tone pulse ona control channel of a magnetic tape associated with the film strip. Unless the duration of energization of the motor is accurately controlled, or electro-mechanical means are employed to stop rotation of the input shaft after a predetermined angular displacement occurs subsequent to energization of the motor, the relative position of the various portions of the drive will be different each time energization of the motor is terminated. This situation raises the possibility of double indexing or failure to index when the tone pulse is detected and the motor is energized. It is to the solution of this problem that the present invention is directed.

Briefly, the invention involves coupling an input shaft to an output shaft only until the latter is indexed through a fixed angle, and then automatically decoupling the input shaft in order to permit it to continue to rotate without imparting further angular displacement to the output shaft. In this manner, the duration of energization of the motor United States Patent 3,552,234 Patented Jan. 5, 1971 is not a factor in securing proper operation of the film index mechanism.

The more important features of this invention have thus been outlined rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will also form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures for carrying out the several purposes of this invention. It is important, therefore, that the claims to be granted herein shall be interpreted with sulficient breadth to prevent the appropriation of this invention by those skilled in the art.

For a fuller understanding of the nature and objects of the invention, reference is made to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a block diagram of a conventional film strip projector utilizing a synchronized magnetic tape to provide audio accompanyment;

FIG. 2 is a sectional view, with parts broken away to show details of construction, of a film drive incorporating the present invention;

FIG. 3 is a front view of the housing, with the cover removed, showing the relative positions of the various parts just prior to energization of the motor;

FIG. 4 is a front view similar to FIG. 3, but showing the relative positions of the various parts just after energization of the motor;

FIG. 5 is a front view taken along the line 55 of FIG. 2 and showing the relative position of the various parts with the motor still energized.

FIG. 6 is a section view taken along the line 6-6 of FIG. 2.

Referring now to FIG. 1, reference numeral 10 designates a film strip projector which is shown in block diagram form to illustrate the environment for the present invention. Basically, the projector includes a film strip magazine 11 which presents one frame at a time to a framing aperture (not shown) aligned with a light source 12 which projects light through the framejinto a projection lens system 13- and onto a screen for viewing. Associated with magazine 11 is a magnetic tape cartridge containing two-channel tape. One channel provides the audio accompanyment for the frame of the film strip being projected; and the other, or control channel, provides cues for indexing the film strip. Such cues are in the form of a tone signal of predetermined duration and frequency. The cue detector 14 reads the control channel of the tape; and when a cue is detected, the tone signal is amplified by control device 15 and applied to electric motor 16 of the film drive 17. The shaft 18 of motor 16 constitutes the input shaft to film mechanism 19 and the shaft 20 of the latter constitutes the output shaft of the drive mechanism. Shaft 20 is connected to a sprocket wheel or pawl (not shown) which actually indexes the film strip in a conventional manner. The feedback link indicated at 20' between the output shaft 20 and control device 15 is a schematic representation of the function served by a conventional electro-mechanical arrangement, or the invention disclosed in detail hereinafter, for

the purpose of accurately limiting the output shaft to a precise angular displacement each time the motor is energized.

Film drive 17 is shown in detail in FIG. 1, to which reference is now made, and is very similar to Model SGM2589 1 manufactured by Molon Motor and Coil Corporation of Rolling Meadows, 111. Motor 16 may be a two pole, shaded pole, AC motor of the type having a shaft 18 axially movable from an inoperative position (shown in phantom lines in FIG. 2) to an operative axial position (shown in solid lines in FIG. 2).

Spring 18' biases shaft 18 toward its inoperative position. Energization of the field winding 21 of the motor causes shaft 18 to begin to rotate, and to move axially against the bias spring from inoperative to operative axial position. It remains rotating in the operative axial position until the field winding is de-energized.

Shaft 18 has armature 44 intermediate its front free end 22 and its rear free end 45. Rigidly fixed to the pole pieces 46 of the motor is a rear bearing mount 47 and a forward bearing mount 48. A recessed boss 49 on the lower portion of well 28 of cup-shaped housing 29 contains the bearing mount 48 which slideably receives shaft 18 intermediate pinion 23 adjacent the free end 22 of the shaft, and armature 44. The free end 45 of shaft 18 is slidably received in rear bearing mount 47.

When shaft 18 is in its operative axial position, it is in relative positon to mesh with teeth 24 of spur gear 25 which is rotatably mounted at its central hub 26 by pin 27 fixed to bottom wall 28 of housing 29. The housing has peripheral side walls 30 containing other components of the film drive mechanism 19. When the motor is deenergized, shaft 18 moves to its inoperative axial position, and pinion 23 is out of the path of tooth 24.

As shown best in FIGS. 3, 4 and 5, spur gear 25 has a portion 38 of its periphery 39 free of teeth. When the gear is in its first angular position, portion 38 is in the fourth quadrant as the front face 32 of the gear is viewed (see FIG. 3). In such angular position, teeth 24 of gear 25 will be engaged by pinion 23 as shaft 18 moves axially in response to initial energization of motor 16. Pinion 23 will thus mesh with gear '25; and continued energization of the motor will start the gear rotating in a clockwise direction as the front face 32 of the gear is viewed. From this standpoint, the meshing teeth on pinion 23 and gear 25 can be considered as being first cooperable means on the input shaft and gear responsive to initial energization of the motor, when the gear is in its first angular position, for starting rotation of the gear in one direction away from its first angular position. As energization of the motor 46 continues, gear 25 continues to rotate clockwise,

as viewed in FIGS. 3, 4 and 5, until it has rotated through a predetermined angular displacement at which portion 38 of the gear is aligned with pinion 23 (FIG. 5). When this occurs, gear 25 and pinion 23 are unmeshed, and no further rotation of the gear by the pinion is possible. For reference purposes, the angular position of the gear at which portion 38 is aligned with the axis of shaft 18 is termed the second angular position of the gear. As long as the gear remains in this angular position, rotation of pinion 23 cannot inpart further rotation to gear 25. For this reason, the teeth on the pinion and the untoothed portion of gear are considered as second cooperable means on the input shaft and gear for limiting rotation of the gear to a predetermined angular displacement less than 360 degrees independent of continued energization of the motor.

In addition to spur gear 25, mechanism 19 includes pawl 31 eccentrically mounted on the front surface 32 of gear 25 by means of pivot pin 33 fixed to face 32 of the gear. The axis of pin 33 is thus parallel to the axis of pin 27 about which gear 25 rotates. Pawl 31 is angularly shaped with a main portion 34 containing a bearing for pin 33, and a remote inclined portion 35 at whose free end 36 is notch 37. The dimensions and configuration of the pawl, combined with the location of pin 33 on face 32 are such to cause free end 36 of the pawl to extend beyond the periphery 39 of spur gear 25 when the latter is in its second angular position (FIG. 5).

Notch 37 receives drive extension 40 on free end 22 of the pinion when gear 25 is in its second angular position and the motor is energized causing shaft 18 to occupy its operative axial position. Clockwise rotation of gear 25 (see FIG. 5) out of its second angular position is prevented by the engagement of notch 37 with drive extension 40. Counter clockwise rotation of gear 25 is prevented by reason of spring 41, one end of which is fixed to pin 42 rigidly mounted on bottom wall 28 of housing 29, and the other end of which is fixed to the end of portion 34 of the pawl 31 remote from pin 33. When the gear is in its second angular position (FIG. 5), spring 41 exerts a clockwise torque upon gear 25 thus seating drive extension 40 firmly in notch 37. In this manner, gear 25 is held in its second angular position as long as the motor is energized.

When the motor is de-energized, shaft 18 moves from its operative position at which drive extension 40 is engaged with notch 37 to its inoperative position at which the drive extension is withdrawn from notch 37, and pinion 23 is moved clear of teeth 24 (see phantom lines in FIG. 2). Gear 25 is now free of constraint and can move out of its second angular position. Spring 41, still exerting a clockwise torque on the gear, is effective to complete rotation of the gear from its second angular position (see FIG. 5) to its first angular position (FIG. 3) by causing the gear to rotate in the same direction that pinion 23 had previously been effective to rotate the gear. In this manner, the gear completes a full cycle of rotation of 360 degrees. From the above description, it can be seen that the pawl and its spring constitute return means on the gear responsive to de-energization of the motor for rotating the gear from its second angular position back to its first angular position in a clockwise direction.

From the above description, it can be seen that the angular displacement of the gear through 360 degrees has two components; a first component is the clockwise angular displacement of the gear from its first to its second angular position, and this displacement takes place in response to energization of the motor; the second component is the clockwise angular displacement of the gear from its second to its first angular position, and this takes place in response to de-energization of the motor and the influence of the spring acting on the pawl. While the drawing shows the first component of displacement to be about 225 degrees, it is believed apparent that other displacements could be used, and in fact, the displacement selected depends on many factors not relevant to the present invention. The only limitation on the magnitude of the first component of angular displacement is the requirement that it be no less than the angular displacement required to actuate Geneva drive 43 which s the last component of drive mechanism 19. The present invention also requires that the motor be energized during an interval no shorter than the total time required for the input shaft to move from its inoperative position to its operative position, and for the pinion to drive the spur gear through an angle sufiicient for actuation of the Geneva drive to occur.

Referring now to FIG. 2, Geneva drive 43 comprises Geneva wheel fixed by a central hub 51 to output shaft 20 which is mounted in a pair of bearings 52 and 53. Bearing 52 is pressed into boss 54 in bottom wall 28 at a location spaced from recessed box 49 which receives the forward bearing mount for the input shaft. Bearing 53 is pressed into a suitable aperture in housing cover 55 which is bolted or otherwise fixed to the free ends of peripheral side walls 30 of the housing. Thrust Washer 56, held by snap ring 57 mounted in a groove shaft 20, abuts the outside of boss 54, and limits axial movement of the shaft in a forward direction. Hub 51 on wheel 50 abuts bearing 52, and thus limits axial movement of the output shaft in a rearward direction.

Geneva drive 43 also includes cam 58 integrally formed on the rear face 59 of gear 25. As shown in FIGS. 3, 4, and 5, a 4-slot wheel is used to develop a 90 degree indexing of the output shaft each time gear 25 rotates from its first to its second angular position. Such indexing is achieved by reason of the cooperation of pin 60 fixed to the rear face 59 of gear 25, with one of the slots 61 in wheel 50. Concave portions 62 of wheel 50 located between slots 61 are designed to ride on the circular portion 63 of cam 58 at all times except when pin 60 is engaged in a slot 61. When this event occurs, cam 58 is relieved as shown at 64 to provide clearance for the free ends 65 of wheel 50 containing slot 61, as shown best in FIG. 4.

To permit framing to take place, the attitude of output shaft 20 in its first angular position must be made adjustable relative to the fixed housing 70 of the projector. This is accomplished by suspending film drive 17 on housing 70 for pivotal movement concentric with shaft 20 as shown in FIG. 2. Accordingly, cover 55 is provided on its exposed surface with an annular bearing ring 68 which is concentric with shaft 20. Ring 68 is frictionally received in bearing groove 69 defined by an inwardly projecting boss on housing 70. Hub 68 on cover 55 projects through aperture 71 in housing 70 and terminates in knob shaft 67 to which a knob (not shown) can be rigidly attached. Framing is achieved by the manual rotation of the knob on shaft 67 against the frictional engagement between ring 68 and groove 69. Such manual rotation is effective to pivot drive 17 on projector housing 70 and change the attitude of shaft 20 relative to the housing. Pin 72 on cover 55 is received in an arcuate slot opening into aperture 71 and serves to limit the angular adjustment of the output shaft 20.

What I claim is:

1. A drive mechanism comprising:

(a) motor means having an input shaft thereon and energizable for causing said input shaft to rotate as long as the motor means is energized;

(b) a rotatable driver;

(c) first cooperable means on said input shaft and driver responsive to initial energization of said motor means, when said driver is in a first angular position, for starting rotation of said driver in one direction away from said first angular position;

(d) second cooperable means on said input shaft and driver for limiting rotation of said driver to a predetermined angular displacement less than 360 independent of continued energization of said motor means, whereby said driver is held in a second angular position while said motor means is energized;

(e) return means on said driver responsive to deenergization of said motor means for rotating said driver from said second angular position back to said first angular position in said one direction.

2. A drive mechanism according to claim 1 in combination with an indexable Geneva drive having an output shaft, said Geneva drive being responsive to rotation of said driver through said predetermined angular displacement for indexing said Geneva drive and rotating said output shaft through a fixed angular displacement each time the motor means is energized independently of the duration of energization of said motor means.

3. A drive mechanism according to claim 2 wherein said driver is in the form of a spur gear, and said input shaft has a pinion thereon and is axially movable from an inoperative axial position, at which the teeth of the pinion and gear are disengaged, when the motor is deenergized, to an operative axial position, at which the teeth of the pinion and gear are in relative position to mesh, when the meter is energized, said g'ear having a portion of its periphery free of teeth so that the gear can be driven by the pinion only until the gear is in said second angular position at which said portion of said gear is aligned with said pinion, whereby the pinion can continue to turn due to continued energization of said motor means without causing further angular movement to said gear.

4. A drive mechanism according to claim 3 wherein the free end of said input shaft has a drive extension that projects beyond the face of said gear when said input shaft is in its operative axial position, and said return means includes a pawl mounted on the face of said gear for pivotal movement about an axis parallel to the axis of rotation of said gear, said pawl having a notch and being mounted on said gear in such position that said notch engages said drive extension when the input shaft is in its operative position and said gear is in its second angular position for holding the gear against further rotation in the one direction.

5. A drive mechanism according to claim 4 wherein said return means also includes a spring acting on said pawl for urging said gear in the one direction when the input shaft is in its operative axial position and said gear is in its second angular position whereby the spring is effective to rotate the gear in the one direction from its second angular position to its first angular position when said motor means is deenergized and said drive extension is retracted from said notch.

6. A drive mechanism according to claim 5 wherein the first angular position of said gear is such that the teeth on the pinion and gear mesh when said motor means is energized.

7. A drive mechanism according to claim 6 wherein said Geneva drive includes a Geneva wheel fixed to said output shaft, and a pin attached to the face of the gear opposite to the face on which the pawl is mounted, said pin being operably engageable with the Geneva wheel when said gear is rotated through said predetermined angular displacement for indexing said output shaft.

8. A drive mechanism according to claim 1 in combination with a film strip projector comprising an indexable film strip having a plurality of frames, said combination including means responsive to rotation of said driver from its first angular position to its second angular position for indexing one frame of said film strip.

9. A drive mechanism comprising:

(a) Motor means having an input shaft thereon and energizable,for causing said input shaft to rotate as long as the motor means is energized;

(b) a rotatable driver;

(c) first means on said driver responsive to rotation of said input shaft by said motor means, when said driver is in a first angular position, for starting rotation of said driver in one direction away from said first angular position;

((1) second means on said driver for limiting rotation of said driver to a predetermined angular displacement less than 360 degrees independent of continued energization of said motor means whereby said driver is maintained in a second angular position while said motor means is energized;

(e) return means on said driver responsive to de-energization of said motor means for rotating said driver from said second angular position back to said first angular position in said one direction.

10. A drive mechanism according to claim 9 wherein said second means further includes a pawl for maintaining said driver in said second angular position while said motor means is energized.

11. A drive mechanism in accordance with claim 9 including an indexable Geneva drive having an output shaft, the Geneva drive being responsive to rotation of said driver through said predetermined angular displacement for indexing said Geneva drive and rotating said output shaft through a fixed angular displacement each time the motor means is energized independently of the duration of energization of said motor means.

12. A drive mechanism according to claim 11 wherein said driver is in the form of a spur gear, and said input shaft is axially moveable from an inoperative axial position when the motor is dc-energized to an axial operative position when the motor is energized, means for mechanically connecting said input shaft to said spur gear, said spur gear having a portion of its periphery free of teeth so that the gear can be driven by the pinion only until the gear is in said second angular position at which that portion of said gear is disengaged from said connecting means whereby the pinion can continue to turn due to continued energization of said motor means without causing further angular movement to said spur gear.

References Cited UNITED STATES PATENTS FRED C. MATTERN, IR., Primary Examiner F. D. SHOEMAKER, Assistant Examiner US. Cl. X.R. 

